"A romantic relationship blossomed as they spent time writing together," a friend of Lavigne tells the mag. Another source tells People, "He makes her so happy. Both of their families could not be more excited."

Kroeger popped the question on August 8 with a 14-carat diamond. (Yowza!)

This will be Chad's first time swapping vows and Avril's second time walking down the aisle, after wedding Sum 41 frontman Deryck Whibley in 2006 and then divorcing in 2009. Lavigne's last relationship was an on-again, off-again romance with Brody Jenner.